Abstract

[Abstraact]: In irrigated environments the uniformity of the water application has a major effect on the soil water content and the subsequent spatial variation in crop stress and yield. However, the evaluation of sprinkler irrigation uniformity using traditional catch can analyses is resource prohibitive and commonly results in only small grids being used to infer whole field performance. A trial was established in a lettuce crop irrigated with a solid set sprinkler system to evaluate the potential to use electromagnetic sensing for irrigation performance assessment. After crop establishment, the uniformity of the irrigation applications was deliberately modified within one sprinkler plot (9 m x 11 m) by reducing the sprinkler operating pressures. The uniformity of the water applied at each irrigation was measured using a grid of catch cans. The apparent soil electrical conductivity (ECa) was measuredwithin the plot at multiple times during the cropping season using an EM38 (Geonics Ltd Canada). The ECa was found to be poorly correlated with the applied irrigation depths prior to sprinkler modification when the uniformity of the irrigations was relatively high. However, the correlation improved after sprinkler modification due to the increasing differences in soil moisture. There wasgenerally a poor relationship between the volumes applied at each irrigation and the difference in ECa measured before and after irrigation. However, this relationship was marginally better for the irrigations immediately after sprinkler modification. This data suggests that EM sensing may be used to identify the spatial variations in irrigation application where the irrigation uniformity is poor (i.e. CU < 70%) and the application patterns are consistent throughout the season but that the technique isnot suitable to evaluate individual application events or where the irrigation uniformity is comparatively high.